This application claims the benefit of Danish Application No. PA 2003 00182 filed Feb. 10, 2003.
The present invention relates to a conveyor belt especially for use in the fresh food production industry as well as a chain link for constructing such a conveyor belt.
In slaughterhouses and abattoirs the butchering of animals is highly industrialized and during the process the animals or part of the animals are transported for example from storage to different stages where the actual cutting of the animals into the desired sections/pieces takes place. During this process, the parts of the animals or lumps of meat are transported on conveyor belts.
These conveyor belts are often 60 cm wide or more so that the entire carcass of an animal or parts thereof will fit onto the conveyor belt. At the same time it is desirable to butcher the animals directly on the conveyor belt as they pass the workstation. For this purpose specialized conveyor belts have been developed where the surface is relatively flush and the independent chain links are assembled in such a manner that the gaps and slices between each link are minimized.
Furthermore, in order to reduce the costs of manufacturing the chain links which make up a conveyor belt, the chain links are often made in an size where, in order to assemble a conveyor belt that is 60 cm or more wide, a number of chain links in the width direction of the conveyor belt is needed. The conveyor belt is hereby assembled by a number of chain links, for example 7 or 8, making up the entire width of the belt and the adjacent row of chain links is assembled in a staggered manner such that a brick laying pattern is constructed.
The chain links are usually assembled by providing protruding eye parts in both the front and rear end of each chain link, such that an eye part alternates with a recess substantially corresponding in size to the width of the eye part. Furthermore, the eye parts are offset on the rear side in relation to the eye parts on the front side of each chain link.
Furthermore, approximately in the middle of each eye part in a transverse direction in relation to the traveling direction of the conveyor belt, an aperture is provided through all the eye parts in each chain link. By overlapping the eye parts including the apertures in a rear side of one chain link with the eye parts and apertures of an adjacent chain link""s front edge, a through going aperture across the width of the conveyor belt is achieved. A pin is thereafter inserted through all the apertures whereby the two chain links become coupled in a hinge like manner.
In the food producing industry and especially in slaughterhouses and abattoirs the hygienic requirements are very strict in order not to contaminate the fresh meat being produced in such places. It is, therefore, necessary that a high degree of cleaning of the conveyor belt is achieved. In order to facilitate this the eye parts and pin members of the conveyor belt are exposed in such a manner that they can be cleaned with high pressure water, steam or the like.
In other applications the conveyor belt is partly disassembled and lowered into chemical rinsing baths, for example over night, in order to assure that no contamination from bacterial growth in the chain link will cause contamination of the meat to be processed on the conveyor belt.
In order to be able to cut the meat directly on the conveyor belt, the top surface of each chain link has a certain size in the transport direction such that a level and stable work surface is provided. In order for this surface to be sufficiently strong in order to withstand the extra force exerted on the surface due to the working of the meat, a supporting ridge is sometimes provided on the underside for supporting the conveyor belt on the conveyor construction.
Some of the problems with the prior art conveyor belts as discussed above is the fact that in the conveyor belt""s width direction the conveyor belt is made up of a number of independent chain links. Between each chain link there will be a gap wherein cut off meat particles and other substances will be able to accumulate. Furthermore, these gaps between the independent chain links are also difficult to rinse in that they usually are very narrow, which makes it difficult for high pressure water jets to flush everything away in that the high pressure source has to be directed perfectly parallel to the slit in order to be able to penetrate the slit and achieve a cleaning action of said slit.
Another disadvantage with the assembly of the conveyor belt from a number of chain links in the width direction is that a number of chain link end sections are comprised in such a conveyor belt. When a part of an animal to be butchered is transported from one conveyor belt onto another conveyor belt, the meat lump will often fall from one conveyor belt to the next conveyor belt. During this fall, on impact with the lower lying conveyor belt it will exert a comparatively high force on to the lower lying conveyor belt. Often the first point of impact for such a lump of meat will be a corner of one of the many chain links. Due to the relatively fragile construction of the free corners of the chain links, these will often break off. These loose plastic chips afterwards present the danger of ending up in the finished meat product, and furthermore the damage of the chain link needs to be repaired. The same problem can arise due to the working process of the butchers working along the conveyor belt in that during their work routines they might accidentally hit the conveyor belt with a tool such that a corner breaks off.
Furthermore, as the butchers cut the meat directly on the belt, the knives can get stuck in the gaps between the chain links. This gives rise to two main problems. The knife can be pulled out of the hand of the butcher, and due to the resilient nature of the blade it might loosen itself from the belt and fly off with the risk of injuring someone. Alternatively, when the knife becomes stuck in the gap a part of it might break off thereby give rise to the danger that the part ends up in the finished products. If it is detected, the conveyor belt and thereby the entire production must be stopped while the knife or part of the blade is recovered.
The invention sets out to alleviate these and other disadvantages by providing a conveyor belt of the type discussed above, which is special in that the belt in a direction perpendicular to the traveling direction of the belt is made from one single chain link, and that the transport top surface comprises a wide main portion and the top part of the eye projections which are flush with the main portion, such that the belt surface is substantially without apertures and/or openings and further that the hinge-like assembly arrangement is fully accessible only from the underside of the belt.
By this inventive chain link is achieved that the narrow gaps between each assembled chain link in the prior art is not present such that from a hygienic point of view it becomes much easier to clean the entire conveyor belt satisfactory in that for each chain link, which usually constitutes 40-60 mm of the total length of the conveyor belt, which altogether, especially for deboning lines, might be 300-400 meter long, no gaps are present This in turn gives the added security that the multitude of gaps, and for the example mentioned above it would be more than 30,000 gaps, does not have to be cleaned. This gives rise to a substantial increase in the confidence that a satisfactory cleaning process complying with the high hygienic standards in the meat producing business can be achieved.
The chain links being used for the conveyor belts of the type mentioned above are usually made from an injection-molded plastic material. During the molding process and especially the hardening and cooling phase, the plastic material will have a tendency to shrink between 2 and 3%.
The apertures produced in the eye parts is made by inserting a steel pin prior to injecting the moldable material into the injection mould.
After the injected material has begun to harden, the pins are withdrawn whereby the apertures in the eye parts are formed. At the same time, however, the plastic material due to the chemical composition, will give rise to the shrinkage stated above.
When the pin is being withdrawn, the eye parts will tend to shrink around the pin, whereby a rather large force is needed in order to withdraw the pin. A further shrinkage and influence of the pins arises from the fact that the main portion of the chain link between the eye parts on the front and rear edges of each chain link also shrinks 2 to 3%. This again causes increased tension on the pins, especially from the outer edges of the apertures.
It has, therefore, in the art been an accepted compromise that in order to be able to produce the chain links in an economically safe way, i.e. with injection mould of a size resulting in that the shrinkage only will have a minimum effect on the production process, and then on the other hand assemble the rather wide conveyor belt from a number of chain links as discussed above.
The invention, however, in order to alleviate the disadvantages as discussed above with reference to cleaning procedures and hygienic standards as well as the breaking off of corners which may also contaminate the meat products the inventor has developed an injection mould which takes into account the shrinkage of the plastic material such that before removing the pins the apertures and thereby the eye parts on the front and rear edges are brought together corresponding to the 2% shrinkage, whereby the tension on the pins arising from forming the apertures in the eye part is substantially lessened such that it is possible to manufacture chain links with a substantial width.
This also makes it possible in a further preferred embodiment to produce a conveyor belt wherein the distance between the front and rear edges is substantially larger than the projecting eye parts extends in the conveyors traveling direction and that on the underside of each chain link is configured a support ridge arranged centrally and extending substantially across the entire width of the chain link.
Hereby is achieved that the effective working surface is enlarged such that a more stable working surface for the people working along the conveyor belt is provided. This in turn results in better working conditions and a more safe and stable cutting surface and thereby minimizes the risk of damaging both the meat and the workers.
In a further advantageous embodiment of the invention the underside of the chain link slopes away from the base of the ridge, such that the link""s material thickness is greater in the middle of the link than along the front and rear edges. In this manner it is assured that liquids and water, which may assemble on the underside of the chain link during the transport of the chain links on their return trip, will drain from the chain links such that also during the production time in the slaughterhouse a higher degree of hygiene is achieved.
By further shaping the eye parts such that the eye parts are wider in the conveyor belts transverse direction at the top surface and tapers towards the under surface, it is achieved that it becomes easier to flush out pieces of meat or other debris which have accumulated around the eye parts and the pin connecting two adjacent chain links.
This configuration also creates bigger openings which again improves the cleaning action in that more water can be forced through the larger openings between the superposed eye parts.
These openings occur when the chain links in the conveyor belt change direction due to the change in path way, for example when the chain link has to perform its return travel at the underside of the conveyor structure.
Usually, the conveyor belt is strung out between two driving wheels, where the power from the motor is imparted into the conveyor belt which thereby is brought into motion. When the conveyor belt turns around the wheels, each chain link will change orientation in relation to a neighboring chain link and thereby the openings around the eye parts will be provided.
In a still further preferred embodiment a configuration having along the front and rear edges the eye parts has a width perpendicular to the traveling direction smaller than the adjacent recess, and furthermore that the upper side of the eye parts is flush with the upper side of the chain links main portion, a larger effective conveyor belt working area is provided.
In this manner it is provided that the eye parts will fit in the recess provided in an adjacent chain link between two eye parts. Furthermore, by having the top part of the eye part flush with the working surface of the conveyor belt, the assembly of two chain links will provide an effective working area in stead of a connection area with substantially different surface conditions than when the top parts of the eye parts are flush with the working surface.
In order to further provide a stable working surface and a strong chain link the height i.e. the distance between the over side of the chain link and the under side of the ridge, respectively the underside of the eye parts is constant. In this manner the chain link is supported at three distinct points along its extension in the intended travel direction of the conveyor belt.
In view of the injection mould process discussed briefly above, it has been found that advantageous embodiments of the invention are achieved when each link has a width perpendicular to the traveling direction which is between 400 mm and 800 mm, preferably between 500 mm and 700 mm, and most preferably 600 mm, and the thickness of each link perpendicular to the surface is between 4 mm and 28 mm, preferably 7 mm to 20 mm and most preferred 12 mm to 17 mm.
In this manner quite large chain links are provided which by themselves or by arranging another similar conveyor belt alongside can provide conveyor belts with a width corresponding to the requirements in the slaughterhouse with a minimum number of chain links and thereby a minimum number of assembly gaps such that the hygienic standard can easily and more securely be obtained.
Also, in view of the injection molding process and the flexibility of the resulting conveyor belt, it has been found advantageous that between 30 and 40 eye protrusions and the same number of recesses are provided for the 600 mm wide links and that between 20 and 28 eye protrusions and the same number of recesses are provided for the 400 mm wide links and further that between 40 and 60 eye protrusions and the same number of recesses are provided for the 800 mm wide links.
This aspect shall be seen in relation to the forces arising on the pin members which are withdrawn during the injection molding process. As the plastic hardens and cools a shrinkage of about 2-3% as mentioned above will occur in the plastic material and thereby increased tension will be created on the aperture forming pins. With the number of eye parts and therefore number of apertures formed as disclosed in this preferred embodiment an advantageous compromise between the injection molding process and the flexibility and effective top working surface of the resulting conveyor belt is achieved.
Also for the same reasons, i.e. due to the injection molding process, the shrinkage and the desire to provide a large effective working top surface on the conveyor belt it has been found advantageous that the distance in the traveling direction of the conveyor belt, between the apertures in the eye parts in the front edge and the rear edge is between 20 mm and 200 mm more preferably between 30 mm and 175 mm, still more preferred between 40 mm and 125 mm, and most preferred 45 mm to 100 mm.
With chain links within these ranges it has been found that a stable and large top surface is provided for transporting and working the meat and at the same time the diameter of the turning wheels can be kept at a relatively small size and furthermore that the number of hinge assemblies where hygienic and cleaning problems can arise is kept at a minimum.
A chain link for constructing a conveyor belt as set out above is also described. This chain link is special in that the link is manufactured as a single piece in a plastic molding process, preferably injection molding, and further that it has a substantially flush top surface, and that eye parts are arranged along to opposite edges said eye parts top surface being flush with the top surface of the chain link, and that eye parts along one edge are staggered relative to eye parts along the opposite edge, and that the width of recesses formed between adjacent eye parts, at least in the top surfaces plane, substantially corresponds to the width of adjacent eye parts.
Also, the chain link in a further advantageous embodiment is made with a higher point on the top surface. From this high point the top surface can slope down to the front and rear edges of the respective link. The height difference between the high point and the edge should only be a matter of millimeters corresponding to 1-2xc2x0 or just enough to drain the top surface of the chain link.
In a further advantageous embodiment the cleaning of the conveyor belt is facilitated in that means are provided whereby the connection pin can be pushed back and/or forth in a direction perpendicular to the intended traveling direction of the conveyor belt. By this arrangement it is possible to move the pin back and forth such that pieces or other food items which has become stuck in the space provided for play between the pin and the apertures is loosened and can easily and reliably be removed during the cleaning process. These means for pushing the pin back and forth can have different configurations.
In order to further improve the cleaning of the conveyor belt comprising a number of identical chain links, the pin connecting adjacent chain links is longer than the width of the chain links perpendicular to the belt""s intended traveling direction such that an end part of the pin projects beyond the side edge of the chain link. In this configuration it becomes possible to manipulate the connection pin, for example by turning it or pushing it back and forth in order to loosen stuck pieces of for example meat which may either contaminate the products placed on the top surface of the belt or give rise to bacteria growth which again will contaminate meat or other perishable goods placed on the conveyor.
In a further advantageous embodiment at least one abutment member is provided along the path the conveyor belt follows on its return passage such that said at least one abutment member will push the projecting end of the connecting pin flush with the side edge of the chain link. In this manner, the abutment member will push the connection pin such that residue or pieces of meat and the like will be loosened if such has become stuck between the apertures in the chain links and the connection pin.
In a further advantageous embodiment the at least one abutment member is arranged before or in a cleaning station suitable for cleaning the chain links, for example by water jets, steam jets or the like as they pass the cleaning station on the conveyor belt""s return passage. Especially in embodiments where more than one abutment member is arranged such that an abutment member is arranged on either side of the conveyor belt, the pins will be pushed first to one side and thereafter to the other side, which together with the cleaning arrangement will automatically provide a thorough and effective cleaning of the area around and inside the apertures provided in the chain links as well as the connection pin.
In order to further improve the cleaning process a still further embodiment of the invention provides that a vibration unit is brought into contact with the connection pins. The vibrations transmitted to the pin and secondly to the conveyor belt will cause foreign objects, which could otherwise contaminate the conveyor belt, to become unstuck which together with the cleaning process, for example flushing with water, will effectively clean the entire conveyor belt structure.
In a further advantageous embodiment the vibration unit is integral with the abutment member, for example such that when the pin engages the abutment sliding surface, the vibration will, due to the oblique character of the sliding surface, have a different effect and thereby a variation in the amount of vibration transmitted to the foreign objects being stuck in the belt structure which will have an increased effectiveness.
In a further alternative embodiment wheels or rollers are provided for engagement with the connection pin during the return passage of the conveyor belt wheels or rollers pivotable about an axis parallel to the conveyor belt""s intended traveling direction are provided such that the wheels or rollers will engage the pin and push it in a direction perpendicular to the conveyor belt""s intended traveling direction. The wheels or rollers will, when engaging the pin, cause the pin to be pushed a little bit to one side relative to the intended traveling direction of the conveyor belt. Thus the same goal as described above will be achieved in that the movement will expose foreign objects being stuck in the pin or aperture.
In a further advantageous embodiment the same movement is provided by providing angled surfaces in the wheels propelling the entire conveyor belt structure. Usually, these wheels engage the underside of the conveyor belt, for example in the area around the pins. By providing them with an angled surface, they will slightly push the connection pin to one side. By furthermore providing the opposite drive wheel with angled surfaces in the opposite direction, the pins will be brought back into the original position. Furthermore, by the loose structure and the dynamics and nature of a conveyor belt of this type, even though the pins are only brought in one direction they will be repositioned due to the further movement of the conveyor belt itself.
In this still further alternative advantageous embodiment of the invention, drive wheels are provided which engage the conveyor belt""s underside and propels the belt in the traveling direction, for example by gear wheels or the like engaging the underside of the belt such that in order to push the connection pin in a direction perpendicular to the conveyor belt""s intended traveling direction at least one drive wheel is provided with an angled engagement surface or at least some of the teeth of a gear wheel are provided with angled engagement surfaces relative to the pin.